Microwave-assisted modification of activated carbon with cationic surfactants for enhancement of naphthalene adsorption

Polycyclic aromatic hydrocarbons (PAHs) are toxic pollutants harmful to humans. To improve the adsorption capacity of PAHs on activated carbon (AC) from the aqueous system, AC was modified with cationic surfactants through microwave heating. Naphthalene is a typical PAH used as a model pollutant to test the adsorption properties of sample; the sample with the best adsorption performance was named SAC. The SAC was characterized by SEM, FTIR and BET in detail compared with AC. The specific surface area and the average pore size of SAC increased by nearly 100 m² g⁻¹ and 0.14 nm more than the original AC, respectively. The adsorption experiment was carried out by batch technique with variables such as contact time, adsorbent amount, pH and temperature. Results showed that naphthalene was adsorbed rapidly during the first 20 min, and thereafter reached adsorption equilibrium in 40 min. The adsorption kinetics of naphthalene on SAC can be well described by the pseudo-second-order model and the Freundlich isotherm model better fitted the adsorption isotherms of naphthalene on SAC. Naphthalene adsorption process on SAC was spontaneous and temperature was found to negatively affect the adsorption capacity. Furthermore, film diffusion was confirmed the rate limiting step. The π-π stacking electron donor acceptor interaction, hydrophobic interaction and hydrogen bonding may play more key roles in naphthalene adsorption on SAC than AC. Thus, microwave-assisted surfactants modification was proven to be an effective method to enhance the adsorption of naphthalene onto SAC from aqueous solution.